Pybind11: typedef and incompatible function arguments error

[xliuk]

In c++ I defined:

typedef std::tuple<int, int, int> Type;
typedef std::tuple<int, int, int, int> Shape;

class Properties {
public:
	Properties() {}
	Properties(Type t_, Shape s_) : t{t_}, s{s_} {}
        ...
private:
	Type t;
	Shape s;
}

I tried to bind with pybind11 in this way:

PYBIND11_MODULE(pybind_test, m)
{
    py::class_<Type>(m, "Type")
        .def(py::init<>())
        .def(py::init<int, int, int>());

    py::class_<Shape>(m, "Shape")
        .def(py::init<>())
        .def(py::init<int, int, int, int>());

    py::class_<Properties>(m, "Properties")
        .def(py::init<>())
        .def(py::init<Type, Shape>());
        ...
}

When I try to use it on python:

...
>>> type = Type(0,8,1)
>>> shape = Shape(10,10,10,10)
>>> prop = Properties(type, shape)

it gives me this error:

TypeError: __init__(): incompatible constructor arguments. The following argument types are supported:
    1. pybind_test.Properties()
    2. pybind_test.Properties(arg0: Tuple[int, int, int], arg1: Tuple[int, int, int, int])

Any idea on how to solve it?

[jiwaszki]

Hi @xliuk , one way to make it work is to make types opaque. The thing is that you are using typedef of std::tuple, which during compilation substitutes both Type and Shape to tuple -- thus you can see Tuple[...] in signature of the init.
What you need to add on top of your bindings:

typedef std::tuple<int, int, int> Type;
typedef std::tuple<int, int, int, int> Shape;

PYBIND11_MAKE_OPAQUE(Type);
PYBIND11_MAKE_OPAQUE(Shape);

In [1]: import mymodule
   ...: 
   ...: type = mymodule.Type(0,8,1)
   ...: shape = mymodule.Shape(10,10,10,10)
   ...: prop = mymodule.Properties(type, shape)
   ...: 
   ...: print(prop.type, prop.shape)
(0, 8, 1) (10, 10, 10, 10)

Here is more info on it: https://pybind11.readthedocs.io/en/stable/advanced/cast/stl.html#making-opaque-types

[xliuk]

Hi, it works. Thank you so much I really appreaciate it! :)